With the aid of FIGS. 1 and 2 a known grate plate arrangement will first be explained. FIG. 1 is a partial view of a plate arrangement from below and FIG. 2 a section along the line II--II of FIG. 1.
The known plate arrangement for a travelling grate illustrated in FIGS. 1 and 2 comprises plates 1, 1', 1", etc. which bear with their front highly curved portion 2 on a pin 3 (with interposed spacer tube 4) and with their real less curved portion 5 on the following plate (e.g. 1').
The plates are provided with a plurality of through slots 6 which extend in the longitudinal direction of the plate and serve for the passage of gaseous treatment medium (hot gases or cooling air).
To increase the strength each plate is provided at its lower side with two longitudinally extending lateral webs 7, 8 and with a cross web 9 disposed substantially in the centre of the plate. Further reinforcing webs running in the longitudinal direction are denoted by 10 and 11.
To secure the plate 1 in its position on the pin 3 and prevent a pivoting up of the plate (in the clockwise direction in FIG. 2, for instance by increased air pressure or in the lower run of the grate) a holder is provided which consists of substantially three arms 12, 13 and 14. The arms 12 and 13 are secured by means of screws 15, 16 and the arm 14 by means of a screw 17 to the cross web 9. The arms 12 and 13 engage beneath the pin 3 and the arm 14 beneath the following pin 3'. The forwardly directed arms 12 and 13 are laterally offset with respect to the rearwardly directed arm 14 so that between the arms 12 and 13 there is room for the arm 14" of the preceding plate 1".
This known grate plate arrangement has certain disadvantages.
Due to the considerable length between the engagement point of the arm 14 on the following pin 3' (or the spacer tube 4') and the mounting of this arm 14 (screw 17) there is a great leverage which leads to high stress of the mounting point. The screw 17 is subjected both to tension and the shearing stress. If the mounting screw 17 becomes loose during operation under this high stress the plate 1 can partially pivot resulting in an undesirable dropping through of material.
Another constructional disadvantage is that the cross web 9 to which the arm 14 is secured is subjected to bending stress. Finally, another disadvantage is that due to the large number of individual parts and the necessary tightening of several screw connections the assembly of the plates and their holding arms is exceedingly time-consuming and complicated.